Recent development of nanomechanical property measurement

Nanomechanical mapping by atomic force microscopy (AFM) has been developed as the useful application to measure the physical properties of soft materials at nano-meter scale. To date, the Hertz theory was used for analyzing force-distance curves as the simplest model of contact mechanics between elastic bodies. However, the preexisting methods based on Hertz theory do not consider the adhesive interaction in principle, which cannot be neglected in the ambient condition. First, we introduce a new analysis to estimate the elasticity and adhesive energy simultaneously by means of the JKR theory, describing adhesive contact between elastic materials. Secondly, poly(dimethylsiloxane), PDMS, and butyl rubber, isobutene-co-isoprene rubber (IIR), were analyzed to verify the validity of the JKR analysis, the method mentioned above. For elastic samples such as PDMS, the force-deformation (F-delta) plots obtained experimentally were consistent with JKR theoretical curves. Meanwhile, for viscoelastic samples, especially for IIR, the F-delta plots revealed deviations from JKR curves depending on scan velocity and indentation depth. To elucidate the limit of the JKR method, we compared the characteristic behaviors of elastic and viscoelastic materials observed from contact measurement at nano-meter scale.